What is the difference between open() and window.open() in Firefox?

Question

In answering my question Pumbaa80 found a difference between calling open() and window.open(), try the following examples in Firefox

Answer 1

The are in fact the same. Try window.open === open or window["open"] === open. If that yields false to you then you must be in a closure and somecode has defined open.

And of course this stands for all the objects that are member of the global (window) object.